/* Base */
* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}
body {
  font-family: "Inter", sans-serif;
  background: #f3f4f6;
  color: #333;
  line-height: 1.6;
  padding: 2rem;
}
.container {
  max-width: 700px;
  margin: auto;
  background: #fff;
  border-radius: 12px;
  padding: 2rem;
  box-shadow: 0 6px 15px rgba(0, 0, 0, 0.08);
  text-align: center;
}
.title {
  font-size: 2rem;
  font-weight: 700;
  margin-bottom: 2rem;
}

/* Hide radio inputs */
input[type="radio"] {
  display: none;
}

/* Progress bar */
.progressbar {
  position: relative;
  margin-bottom: 2rem;
  padding: 2rem 0;
}
.line {
  position: absolute;
  top: 50%;
  left: 0;
  width: 100%;
  height: 4px;
  background: #e5e7eb;
  transform: translateY(-50%);
  z-index: 1;
}
.line-fill {
  position: absolute;
  top: 50%;
  left: 0;
  height: 4px;
  background: #10b981;
  transform: translateY(-50%);
  z-index: 2;
  width: 0%;
  transition: width 0.3s ease;
}
.steps {
  display: flex;
  justify-content: space-between;
  position: relative;
  z-index: 3;
}
.circle {
  width: 42px;
  height: 42px;
  background: #d1d5db;
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  font-weight: 700;
  color: #111827;
  transition: all 0.3s ease;
  cursor: pointer;
  font-size: 16px;
}
.circle::after {
  content: attr(data-step);
}
.circle:hover {
  transform: scale(1.1);
  box-shadow: 0 4px 12px rgba(0, 0, 0, 0.15);
}

/* Progress line width */
#step1:checked ~ .progressbar .line-fill {
  width: 0%;
}
#step2:checked ~ .progressbar .line-fill {
  width: 33.333%;
}
#step3:checked ~ .progressbar .line-fill {
  width: 66.666%;
}
#step4:checked ~ .progressbar .line-fill {
  width: 100%;
}

/* Step 1 active */
#step1:checked ~ .progressbar .steps .circle:nth-child(1) {
  background: #2563eb;
  color: #fff;
}

/* Step 2 active */
#step2:checked ~ .progressbar .steps .circle:nth-child(1) {
  background: #10b981;
  color: #fff;
}
#step2:checked ~ .progressbar .steps .circle:nth-child(2) {
  background: #2563eb;
  color: #fff;
}

/* Step 3 active */
#step3:checked ~ .progressbar .steps .circle:nth-child(1),
#step3:checked ~ .progressbar .steps .circle:nth-child(2) {
  background: #10b981;
  color: #fff;
}
#step3:checked ~ .progressbar .steps .circle:nth-child(3) {
  background: #2563eb;
  color: #fff;
}

/* Step 4 active */
#step4:checked ~ .progressbar .steps .circle:nth-child(1),
#step4:checked ~ .progressbar .steps .circle:nth-child(2),
#step4:checked ~ .progressbar .steps .circle:nth-child(3) {
  background: #10b981;
  color: #fff;
}
#step4:checked ~ .progressbar .steps .circle:nth-child(4) {
  background: #2563eb;
  color: #fff;
}

/* Panels */
.content .panel {
  display: none;
}
#step1:checked ~ .content .panel1,
#step2:checked ~ .content .panel2,
#step3:checked ~ .content .panel3,
#step4:checked ~ .content .panel4 {
  display: block;
  animation: fadeIn 0.3s ease;
}

/* Animation */
@keyframes fadeIn {
  from {
    opacity: 0;
    transform: translateY(5px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

/* Footer */
.credit {
  margin-top: 2rem;
  padding-top: 1rem;
  border-top: 1px solid #e5e7eb;
}
.credit a {
  text-decoration: none;
  color: #111827;
  font-weight: 600;
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
}
.credit a:hover {
  color: #2563eb;
}
.github-icon {
  fill: currentColor;
}
